The present invention relates to a heat storage type heater which stores heat in a heat-storing material and supplies the heat to different types of heat-utilizing facilities, e.g., for heating and hot-water supply, and a method of controlling input and output of heat to and from the heat storage type heater.
FIG. 10 shows a basic configuration of conventional latent heat storage type heating-devices which utilize the supercooling phenomena of materials (for example, see Japanese Unexamined Patent Application Publication Nos. 62-228822, 3-292214, 6-11145 and 6-281372).
In FIG. 10, a heat-storing material 21, which presents a supercooling phenomenon, is contained in a container 22, the container 22 is provided with a mechanism 23 to which energy is externally supplied so that the supercooled state of the heat-storing material 21 is released, the container 22 is enclosed with a case 25 in which a heat medium 24 is accommodated, and the entire surface or a part of the surface of the case is a heat radiation surface.
In this heat storage type heating-device, first, the heat-storing material 21 is externally heated through the heat medium 24 to be melted. The melted heat-storing material 21 is let to stand as it is till heat is required. When the stored heat is required, energy is supplied to the mechanism 23 for releasing the supercooled state so that the start of the nucleation in the heat-storing material 21 is promoted, and the material 21 is solidified. The heat-storing material 21, after the solidification starts, is recovered to the melting point. The heat at the melting point is radiated to a material to be heated or a space via the heat medium 24 or via the heating medium 24 and the heat radiation surface 25.
The conventional latent heat storage type heating-devices utilizing supercooling phenomena have been proposed in order to compensate a time lag between generation and emission of heat. This is a primary purpose of heat storage. In practice, the function of the devices is liable to stop, due to phase-segregation. Moreover, such a significant difference as expected can not be attained between the melting point and the nucleation temperature (hereinafter, the difference will be referred to as a degree of supercooling in this specification). Thus, the latent heat storage type heating-devices can not be subjected to industrial applications.
That is, in the above-described respective latent heat storage heating-devices, a heat-storing material capable of being supercooled is filled into a large container.
Molecules with different masses are present in the liquid formed by melting the heat-storing material. Molecules with higher masses precipitate downward against the Brownian motion, so that the molecules with higher masses and the molecules with lower masses tend to be segregated from each other. Therefore, as a container for a heat-storing material has a larger length in the direction of gravity, it is more difficult to restore the heavy and light molecules which are separated from each other and react with each other. After the phase-segregation, the melting points and the solidifying temperatures inherent in the respective separated substances appear. Accordingly, in the above-described conventional example, the primary function of the heat-storing material, that is, the melting (solidification) at a particular melting point can not be performed, due to the phase-separation. Moreover, the frequency at which crystal nuclei are formed per unit time and unit volume is determined by the temperature. On the other hand, if nuclei are formed at one site in the heat-storing material, the formation triggers the solidification of the heat-storing material, irrespective of the volume of the heat-storing material. Accordingly, the probability at which the heat-storing material having a predetermined volume is solidified is defined as the product of the volume of the heat-storing material and the frequency of formation of crystal nuclei per unit time and unit volume.
Accordingly, as the volume of the heat-storing material becomes larger at a constant temperature, nuclei are formed more readily, and the degree of supercooling is decreased. For this reason, in the conventional example, such a high supercooling as expected can not be attained, as described above. Thus, the industrial use of the latent heat storage type heating device has not been realized with much troubles.
It is an object of the present invention to provide a heat-storage type heater which solves the above-described conventional problems and can completely compensate a time lag between the input and output of heat, which is a purpose inherent in heat-storage, and to provide a method of controlling the input and output of heat.
Also, it is an object of the present invention to provide a heat-storage type heater by which a desired degree of supercooling can be obtained without the function being stopped due to the phase separation and to provide a method of controlling the input and output of heat.
To achieve the above-described objects, a heat-storage type heater in accordance with the present invention comprises means for supplying heat to a heat-storing material capable of being supercooled, the heat-storing material, together with a phase-segregation preventive agent, being filled into a plurality of small containers, means for releasing the supercooled state of the heat-storing material, and a heat radiation surface.
The means for releasing the supercooled state may comprise a heat exchanger which is disposed so as to be in contact with the containers for the heat-storing material, and circulates a fluid, a thermoelectric element disposed so as to be in contact with the containers for the heat-storing material, a vibrator disposed so as to be in contact with the containers for the heat-storing material, or electrodes disposed so as to be in contact with the containers for the heat-storing material.
Moreover, a heat-storage type heater in accordance with the present invention comprises means for supplying heat to a heat-storing material capable of being supercooled, the heat-storing material being filled into a plurality of small containers together with a phase-segregation preventive agent, and a heat radiation surface. In this case, preferably, the heat-storing material capable of being supercooled spontaneously starts to be solidified at a predetermined temperature in the supercooled state thereof.
Preferably, the small containers have a shape having a smaller size in the gravity direction or a shape elongated in the horizontal direction. The means for supplying heat to the heat-storing material may comprise a heat exchanger which circulates a fluid therein, or an electric heater. Moreover, the surface of the heat-storage type heater except for the heat radiation surface may be covered with a heat insulating material, or the heat-storage type heater may further comprises means for causing forced convection of a fluid on the heat radiation surface so that the heat radiation is accelerated.
The above-described heat-storage type heater can be effectively used for a floor heating system.
Moreover, a method of controlling the input and output of heat to and from a heat-storing material in accordance with the present invention comprises the steps of externally supplying heat energy to the heat-storing material capable of being supercooled and filled into a plurality of small containers together with a phase-separation preventive agent by use of means for supplying heat, whereby the heat-storing material is melted, maintaining the heat-storing material in the supercooled state by emission of heat, and when the stored thermal energy is required, releasing the supercooled state of the heat-storing material by use of means for releasing the supercooled state of the heat-storing material, or allowing the heat-storing material to be spontaneously solidified at a predetermined temperature, whereby the heat at the melting point is generated. When the means for releasing the supercooled state of the heat-storing material is used, the time at which the supercooled state of the plurality of the heat-storing materials can be controlled individually for the heat-storing materials.
Moreover, according to a method of controlling the input and output of heat to and from the above-described heat-storage type heater in accordance with the present invention, after emission of heat from the heat radiation surface of the heat-storage type heater and melting of the heat-storing material are carried out in the heat-storage type heater, the period from the first time at which the means for supplying heat to the heat-storing material is stopped after the emission of heat from the heat radiation surface of the heat-storage type heater and the melting of the heat-storing material are carried out, till the second time at which the heat-storage type heater spontaneously starts to be solidified can be set by using a heat transmittance via the heat radiation surface and the thermal insulating material, and the thermal properties, mass (here, the mass functions as a factor for determining the volume and also as a factor for determining the heat capacitance), and temperature of the heat-storing material.
The heat-storing material (hydrates) capable of being supercooled employed in the present invention has high efflorescent and deliquescent properties and remarkably presents the above-described phase-segregation. Thus, the heat-storage type heater and the heat-storage device can not be realized, if means for tightly closing the heat-storing material for a long time and means for preventing the phase-segregation for a long period are not used. Moreover, as the volume of the heat-storing material becomes larger, it is more difficult from the standpoint of the strength to produce a container for containing the heat-storing material tightly for a long time. Accordingly, the size of the container in the gravity direction needs to be increased, which will cause the phase-segregation.
In the heat-storage type heater in accordance with the present invention, the heat-storing material capable of being supercooled, together with the phase-segregation preventive agent, is contained in a plurality of the small containers. Accordingly, the heat-storing material can be enclosed easily and tightly for a long time. The efflorescence and the deliquescence of the heat-storing material can be easily suppressed. Heavy molecules and light molecules in the heat-storing material separated by melting are further separated from each other in the vertical direction, due to the difference in gravity between the molecules. This motion is suppressed by the added phase-separation preventive agent, and moreover, the reduced size in the gravity direction prevents the thickness of the separation layer from increasing. Thus, the separation can be easily solved. Accordingly, according to the heat-storage type heater of the present invention, the phase-separation of the heat-storage type heater can be prevented from a long time.
The experiment by the inventor has revealed that the degree of supercooling, which is most important for this heat storage system, depends on the volume of the heat-storing material; and as the volume of the heat-storage type heater becomes larger, the degree of supercooling becomes smaller, so that advantages obtained by utilizing the supercooling phenomenon are deteriorated. According to the present invention, the heat-storage type heater is filled into a plurality of the small containers. Thus, the volumes of the heat-storing materials in the respective containers are small, and the frequency per unit time at which crystal nuclei are formed is small. Thus, the heat-storing material is stored while it has a high degree of supercooling. Such high supercooling phenomenon as have not been realized according to conventional propositions can be stably obtained for a long time.